The integrated control of cardiovascular homeostasis is achieved through a combination of both direct neuronal control and systemic neurohormonal activation. Although the resultant release of both contractile and relaxant factors is normally under stringent regulation, an aberration in this status quo can result in cardiohemodynamic dysfunction with pathological consequences.
The principal mammalian vasoactive factors that comprise this neurohumoral axis, namely angiotensin-II, endothelin-1, and norepinephrine, all function via an interaction with specific G-protein coupled receptors (GPCR). The urotensin-II/UT receptor (formerly known as GPR14) system represents a novel member of this neurohumoral axis. As such, inhibitors of this system have the potential to be of utility in the management of a diverse range of diseases.
In studies with human Urotensin-II [Ames et. al. Nature 1999, 401, 282-286; Behm et al., 2004, Naunyn-Schmeid. Arch. Pharmacol., 369; 274-280] it was found that it was an extremely potent and efficacious vasoconstrictor in vitro and in vivo; exhibited sustained contractile activity that was extremely resistant to wash out; and had detrimental effects on cardiac performance (myocardial contractility).
Human Urotensin-II was assessed for contractile activity in the rat-isolated aorta and was shown to be the most potent contractile agonist identified to date. Based on the in vitro pharmacology and in vivo hemodynamic profile of human Urotensin-II in the cat [Behm et al., 2004, Naunyn-Schmeid. Arch. Pharmacol., 369; 274-280), monkey [Ames et. al. Nature 1999, 401, 282-286] and human [Lim et al., 2004, Circulation, 109; 1212-1214] it plays a pathological role in cardiovascular diseases characterized by excessive or abnormal vasoconstriction and myocardial dysfunction [Douglas et al., 2004, Trends Pharmacol. Sci., 25; 76-85].
Compounds that antagonize the Urotensin-II receptor may be useful in the treatment of congestive heart failure, stroke, ischemic heart disease (angina, myocardial ischemia), cardiac arrhythmia, hypertension (essential and pulmonary), COPD, fibrosis (e.g. pulmonary fibrosis), restenosis, atherosclerosis, dyslipidemia, asthma [Hay D W P, Luttmann M A, Douglas S A: 2000, Br J Pharmacol: 131; 10-12, Gilbert et al. 2004, Curr Opin Investig Drugs, 5; 276-282 and Douglas et al. 2004, Trends Pharmacol. Sci., 25; 76-85], neurogenic inflammation and metabolic vasculopathies all of which are characterized by abnormal vasoconstriction and/or myocardial dysfunction. Urotensin antagonists may provide end organ protection in hypersensitive cohorts in addition to lowering blood pressure.
Since Urotensin-II (U-II) is expressed within the mammalian CNS [Ames et. al. Nature 1999, 401, 282; Chartrel et al., 2004; J. Neurochem., 91; 110-118], U-II antagonists may be useful in the treatment of addiction, schizophrenia, cognitive disorders/Alzheimer's disease, [Gartlon J. Psychopharmacology (Berl) 2001 June; 155(4):426-33], impulsivity, anxiety, stress, depression, pain, migraine, neuromuscular function, Parkinson's, movement disorders, sleep-wake cycle, and incentive motivation [Clark et al. Brain Research 923 (2001) 120-127].
Functional U-II receptors are expressed in rhabdomyosarcomas cell lines and therefore U-II antagonists may have oncological indications. [Takahashi et al., 2003, Peptides, 24; 301-306; Matsushita et al., 2003, Endocrinology, 144; 1825-1831; Yoshimoto et al., 2004, Peptides, 25; 1775-1781]. Urotensin II may also be implicated in various metabolic diseases such as diabetes [Ames et. al. Nature 1999, 401, 282; Wenyi et al., 2003, Diabetologia, 46; 972-976] in various gastrointestinal disorders [Horie et al., 2003, Neuropharmacology, 45; 1019-1027], bone, cartilage, and joint disorders/inflammation (e.g. arthritis and osteoporosis; [Bottrill et al., 2000; Br. J. Pharmacol., 130; 1865-1870; Horie et al., 2003, Neuropharmacology, 45; 1019-1027; Suga et al., 2004, J, Biochem., 135; 605-613]; and genito-urinary disorders, including overactive bladder [Yano et al., 1994, Gen. Comp. Endocrinol., 96; 412-419]. Therefore, these compounds may be useful for the prevention (treatment) of gastric reflux, gastric motility, ulcers, arthritis, osteoporosis and urinary incontinence [Yano et al., 1994, Gen. Comp. Endocrinol., 96; 412-419] and obesity [Takahashi K, Endocr J. 2004 February; 51(1):1-17].